Powder coating, method for production thereof, method for using said powder coating and coated article

ABSTRACT

The present invention provides a powder paint excellent in productivity and cost, because the powder paints that are not adhered to the substrate can recovered and reused. And in case of using the powder paint of the present invention, coating efficiency is high and fine textured coated films excellent in attractiveness of appearance and water resistance can be obtained, because the base paint powder and the pigment particle thereof hardly separate. The powder paints of the present invention are characterized in that the pigment particles are bound to the base paint powders via shellac. The powder paints of the present invention not only allows uniform and firm binding of pigment particles to base paint powders by the action of shellac, but also provides the resulting coated films with excellent attractiveness of appearance.

TECHNICAL FIELD

The present invention relates to a powder paint excellent inattractiveness of appearance (particularly, metallic and pearlappearance), a process of producing the same, a process of formingcoated films using the powder paint, a process of producing coatedproducts, and a coated product. In particular, the powder paintsaccording to the present invention are excellent in coating efficiency;provide uniform coated films excellent in attractiveness of appearanceand water resistance; and further are excellent in productivity and costeffectiveness as the powder paints can be recovered and reused.

BACKGROUND ART

Hitherto commonly used for painting is the method of applying a liquidpaint wherein paint ingredients are dissolved in organic solvents onto asubstrate and then evaporating the organic solvent. However, the methodcarries the problem of harmful organic solvent being evaporated, therebyexerting adverse effects on humans and the environment. In order tosuppress the emission of these volatile organic substances (VOC), thereis a trend toward the replacement by powder paints that allow coatingwithout the use of organic solvents. In addition, powder paints have theadvantages that the characteristics thereof can be easily modified byproperly selecting suitable resins from a variety of synthetic resins asthe main component of the paint powders and that the thickness of thecoated films can be freely controlled, allowing coating of thickerfilms.

To these powder paints, pigments having a variety of characteristics areadded as the ingredients for the purpose of improving the attractivenessof appearance of coated films. For example, various powder paints havingnovel characteristics are now under development or in production thatcontain not only extender pigments and coloring pigments for the purposeof providing colors but also bright pigments and phosphorescentpigments.

As the process for producing such powder paints, a method of kneading apigment with a paint, more specifically, a method of melt-kneading apaint composition containing pigments and the like and subsequentlypulverizing the resulting composition (melt-kneading/pulverizationmethod) has been employed.

However, the melt-kneading/pulverization method had the problem that thepigments, especially bright pigments, are broken down duringmelt-kneading, leading to decrease in the attractiveness of appearanceof coated films, as the ingredients are dispersed uniformly by kneadingthe composition under shearing force at the melting temperature of theresins. For example, when an aluminum powder is used as the brightpigment, the aluminum powder is broken down by the shearing force anddiscolored to black or gray during the melt-kneading process.Accordingly, coating of the bright powder paints containing suchbroken-down aluminum powders do not allow production of bright coatedfilms having metal brilliance any more.

To solve the problem, a method wherein the base paint powders are firstproduced by the melt-kneading/pulverization method and then brightpigments or the like are blended to the resulting base paint powders(dry blending method) has been employed in production of such powderpaints. This dry blending method is a method wherein powder paintcompositions, containing resins and, if desired, some additivesincluding coloring pigments and the like, are previously melt-blended togive paint particles, and pigments and the particles are simplymechanically blended without the resins being melted to give powderpaints. Therefore, the pigments are not subjected to high temperatureand great shearing force. As the result, powder paints that retain theoriginal characteristics of the pigments can be produced.

However, the powder paints produced by this method (dry blendingmethod), having relatively lower binding force between the paintparticles and pigments, cause some problems associated with theoperating efficiency during commercial scale coating and thecharacteristics of the resulting coated films. Namely, the separation ofthe paint particles and pigments during the coating operation affectsthe attractiveness of appearance due to decrease in pigments present inthe coated films, or makes the reuse of the recovered paints moredifficult.

For example, when a resin-coated aluminum powder is use as the pigment,the paint particles and aluminum powders in the powder paint separatedue to the difference in electrostatic characteristics during coating byusing an corona discharge electrostatic spray coater, and the aluminumpowders adhere to the voltage application needles and the vicinitythereof located at the tip of the corona discharge electrostatic spraycoater. Consequently, the amount of aluminum powders contained in thecoated films become smaller than that in the original powder paints, andit becomes difficult to obtain coated films having sufficient metalbrilliance and excellent in attractiveness of appearance. Pearlpigments, exhibiting the similar phenomena more profoundly, only providecoated film less attractive in appearance. In addition, the paints thatare not adhered to substrates have a smaller amount of pigments than theoriginal paint and provides only coated films less attractive inappearance, and accordingly cannot be recovered and reused, demandinggreater economic burden especially in production of coated films inlarge quantity. Further, if the masses of pigments adhered onto theneedles or the vicinity thereof of the electrostatic spray coater happento fall on the substrate, protrusions (spits) are formed on the coatedsurface, causing the problem of drastically damaging the appearance ofthe coated film.

As the process of producing powder paints that can solve the problemsassociated with the breakdown of pigments and the spits and providecoated films more attractive in appearance, the “heat mixing method”,whereby the paint powders and pigments are blended while mild heating,was developed. However, as the demands of consumers escalate, the heatmixing method cannot always provide coated films sufficiently attractivein appearance, and accordingly there exists a need for powder paintsthat provide coated films having an attractiveness of appearance at anincreased level.

Incidentally, Japanese Unexamined Patent Publication No. 2002-235039discloses a bright powder paint composition dispersed in a non-aqueoussolvent, wherein the powder paint solid resin particles and brightpigments are dispersed in a non-aqueous medium having insolubility orpoor solubility for the solid resin particles. And this bright powderpaint composition dispersed in a non-aqueous solvent can be recoveredand reused by collecting the oversprayed paints. However, the bondingbetween the powder paint solid resin particles and the bright pigmentsis extremely weak as they are simply blended; if the paints that are notadhered to the substrate are to be recovered and reused, it is unlikelythat the amount of bright pigments in the recovered paints is constantall the time and such recovered paint provides coated films attractivein appearance in such an extent as that of the original films.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a powder paintexcellent in productivity and cost, wherein the base paint powder andthe pigment particle thereof hardly separate, thus allowing high coatingefficiency, production of coated films excellent in attractiveness ofappearance and water resistance, and recovery and reuse of the powderpaints that are not adhered to the substrate. And an object of thepresent invention is to provide a process of producing the powder paint,and a process of using the same.

The present inventors devised earlier a process of producing a brightpowder paint that provides a coated film excellent in attractiveness ofappearance (Japanese Patent Application No. 2002-271904). According tothe method, a bright powder paint wherein a paint powder and aflake-like pigment powder are homogeneously and firmly bound to eachother can be produced by the steps comprising, at least, blending thepaint powder and flake-like pigment (bright pigment); blending theresulting mixture with a liquid bonding auxiliary agent: and drying.Such powder paints have high coating efficiency, allow the recovery andreuse thereof, and provide coated films highly attractive in appearance.

After an intensive study to further improve the method above, thepresent inventors have found that the use of a shellac solution as abonding auxiliary agent allows production of coated films smaller inunevenness and excellent in attractiveness of appearance and waterresistance, and that the beneficial effect thereof can be used forimprovement of other powder paints that contain pigments other thanbright pigments, and completed the present invention.

Namely, the powder paints according to the present invention arecharacterized in that the powder paints are excellent in attractivenessof appearance and the pigment particles therein are bound via shellac tothe base paint powders therein. The powder paints according to thepresent invention, wherein the pigment particles are uniformly andfirmly bound to the base paint powders due to the composition above,show a high coating efficiency, provide coated films excellent inattractiveness of appearance and water resistance, and allows therecovery and reuse of the powder paints that are not adhered to thesubstrate.

The content of shellac in this powder paint is preferably 0.01 to 1 mass% with respect to the total amount of the powder paint. It is becausethe presence of shellac within this range leads to higher dispersion ofthe ingredients and more favorable evenness of the resulting coatedfilms and provides coated films further more improved in attractivenessof appearance.

The average diameter of the base paint powders is preferably 10 to 100μm, and the average diameter of the pigment particles is preferably notmore than 100 μm.

With the average diameters in these ranges, the binding between thepigment particles and base paint powders become more uniform under theaction of shellac, and the coated surfaces become more attractive inappearance. Typical examples of the pigment particles include brightpigments having an average diameter of 2 to 100 μm, especially brightpigments in the shape of flake having a thickness of 0.01 to 10 μm;inorganic coloring pigments having an average diameter of 0.01 to 5.0μm; organic coloring pigments having an average diameter of 0.01 to 1.0μm; and phosphorescent pigments having an average diameter of 1 to 100μm; and these pigment particles may be used alone or in combination oftwo or more.

The content of the pigment particles with respect to the total amount ofthe powder paint is preferably 0.1 to 50 mass %. It is because thepigment particles present in the amount within this range increase theattractiveness of appearance more efficiently.

The process of producing powder paints according to the presentinvention is characterized in comprising the steps of: blending the basepaint powder and the pigment particle; blending the resulting mixturewith a liquid bonding auxiliary agent wherein shellac is dissolved in anorganic solvent; and drying. The aforementioned powder paints can beproduced in the process comprising least these steps.

In the aforementioned step of blending a liquid bonding auxiliary agent,a mechanically agitating blender or airstream fluidized blender isgenerally used.

The liquid bonding auxiliary agent is preferably added by spraying ordropwise addition. By such a adding method, the liquid bonding auxiliaryagent can be added uniformly in smaller portions to the mixture of thebase paint powders and pigment particles, thus allowing uniform bindingof the pigment particles to the base paint powders.

When the bonding auxiliary agent is added by spraying, it is preferableto use the mode wherein the step of spraying the liquid bondingauxiliary agent is carried out concurrently with the step of drying bysupplying air. It is because by in this manner the adhesion and bindingbetween the pigment particles and the base paint powders proceedsimultaneously, allowing production of the powder paint in a shorterperiod. In such a case, the use of heated air as the air enables evenfaster production.

The process of forming coated films according to the present inventionis characterized in that the coated film is formed by electrostaticpowder coating of the powder paint described above onto a substrate madeof metal material. According to the process, the base paint powders andthe pigment particles do not separate and provide uniform coated filmshighly attractive in appearance, even by the electrostatic powdercoating method that is suitable for metal substrates but tends to causeseparation of pigment particles from the base paint powders.

A primer layer is preferably formed in advance to the electrostaticpowder coating. The presence of the primer layer between the metalmaterials and the coated films can increase the corrosion resistance anddurability of the metal materials. In addition, the presence of acolored primer layer could further increase the attractiveness ofappearance, selecting proper combination of the color with the hue ofthe base layer.

The use of powder paint for forming of the primer layers can lead toreduction in the emission of harmful volatile organic substances.

The powder paint to be used for forming the primer layers is preferablythose having epoxy resin hardening-type polyester resins or acidhardening-type epoxy group-containing acrylic resins as the maincomponent of the base paint powder. The use of these powder paintsallows formation of hardened coated films, and especially the use of theformer resins provides coated films excellent in corrosion resistance,and the latter, in weatherability.

In the process of forming coated films described above, it is preferableto form a top clear layer as the utmost outer layer. Such a top clearlayer further increases the appearance of the coated films such asbrilliance and evenness and the performance of the coated filmsincluding weatherability, or the like.

Preferably, the top clear layers are formed with an acrylicsolvent-based clear paint or an acrylic powder-based clear paint: theacrylic solvent-based clear paint is preferably polyisocyanatehardening-type clear paint; while the acrylic powder-based clear paintis acid hardening-type clear paint having epoxy groups, or those havingepoxy group-containing acrylic resins as the main resin and containing apolycarboxylic acid (preferably, dodecanedicarboxylic acid) as a curingagent. The acrylic solvent-based clear paints are excellent inweatherability, while the acrylic powder-based clear paint is excellentin weatherability and at the same time allow reduction in the emissionof harmful volatile organic substances.

The process of producing coated a product according to the presentinvention is a process of producing a coated product coated with apowder paint characterized in comprising a step of coating theaforementioned powder paint onto a substrate made of metal material byelectrostatic powder coating. The process of producing a coated productaccording to the present invention is an application of the process offorming coated films described above and has similar characteristics tothe process of forming coated films described above. Additionally, thesuitable embodiments of the process of producing coated productsdescribed above may be applied to the process of producing coatedproducts according to the present invention, and the same is true forthe operation and effect thereof as well.

Further, the coated product according to the present invention ischaracterized in being produced by the method described above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The largest advantage of the powder paint according to the presentinvention is that the pigment particles are bound uniformly to the basepaint powders and thus the powder paint provides coated film of fine anduniform texture excellent in attractiveness of appearance. If the basepaint powders and the pigment particles, two main ingredients of thepowder paint, are distributed unevenly, colored pigments provide coatedfilms having a mottled appearance, and phosphorescent pigments thosethat cannot emit light uniformly. Particularly in the case of brightpigments, the resulting coated films have black spots, which cannotreflect light, due to the absence of pigments. Coated films have agreater these spots are less attractive in appearance. On the otherhand, uniform and firm binding between the pigment particles and basepaint powders in the powder paint of the present invention preventsfacile separation of the pigment particles from the base paint powdersduring coating, and thus provides coated films strikingly moreattractive in appearance. Furthermore, the powder paint of the presentinvention not only allows recovery and reuse but also provides coatedfilms excellent in water resistance.

Hereinafter, the embodiments and technical merits of the presentinvention for offering the advantages described above will be described.

First, the “base paint powder” used in the present invention will bedescribed.

The “paint powders” used as the “base paint powders” of the presentinvention are those used conventionally as powder paints, which areproduced by melt-blending a paint composition containing a film-formingresin, and added if desired a coloring pigment, an extender pigment andother additives, and pulverizing the resulting compound into powders,according to any one of the processes known in the art.

The “film-forming resins” used as the paint powders includethermosetting resins, thermoplastic resins, and the like commonly usedhitherto as the film-forming resins for powder paints, but are generallythermosetting resins. Examples of the “thermosetting resins” include:(i) combinations of a hydroxyl group-containing solid resin and a curingagent having functional groups that cause a hardening reaction with thehydroxyl groups under heat; (ii) combinations of a carboxylgroup-containing solid resin and a curing agent having functional groupsthat cause a hardening reaction with the carboxyl groups under heat; and(iii) combinations of an epoxy group-containing solid resin and a curingagent having functional groups that cause a hardening reaction with theepoxy groups under heat. The “solid” resin means a resin that is insolid state at room temperature, preferably having a softening point of80 to 200° C. The curing agents to be used may be solid or liquid, butare preferably solid.

As the “hydroxyl group-containing solid resins”, publicly known resinscommonly used for powder paints such as hydroxyl group-containingacrylic resins and hydroxyl group-containing polyester resins can beused. As the “curing agents having functional groups that cause ahardening reaction with hydroxyl groups under heat” to be used incombination with the hydroxyl group-containing solid resins, publiclyknown curing agents commonly used for powder paints such as blockedpolyisocyanate compounds and aminoplast resins may be used.

As the “carboxyl group-containing solid resins”, publicly known resinscommonly used for powder paints such as carboxyl group-containingacrylic resins and carboxyl group-containing polyester resins may beused. As the “curing agents having functional groups that cause ahardening reaction with carboxyl groups under heat” to be used incombination with the carboxyl group-containing solid resins, publiclyknown curing agents used for powder paints: for example, epoxy resinssuch as bisphenol A—epichlorohydrin-type epoxy resins, alicyclic epoxyresins, novolak-type epoxy resins, and epoxy group-containing acrylicresins; hydroxyalkylamide compounds; and the like may be used.

As the “epoxy group-containing solid resins”, publicly known resins usedfor powder paints: for example, bisphenol A—epichlorohydrin-type epoxyresins, alicyclic epoxy resins, novolak-type epoxy resins, epoxygroup-containing acrylic resins, and the like may be used. As the“curing agents having functional groups that cause a hardening reactionwith epoxy groups under heat” to be used in combination with the epoxygroup-containing solid resins, publicly known curing agents used forpowder paints: for example, carboxyl group-containing polyester resins,organic acid polyhydrazide compounds, imidazole compounds, dicyandiamidecompounds, polycarboxylic acid compounds, acid anhydrides, and the likemay be used.

Among thermosetting resins exemplified above, the following combinationsare preferable as they allow production of coated films excellent inperformance (weatherability, or the like), finish (attractiveness ofappearance, smoothness, or the like.), or the like.

(iv) Combination of a Hydroxyl Group-Containing Polyester Resin and aBlocked Polyisocyanate Compound

The hydroxyl group-containing polyester resins to be used are preferablythose having a hydroxyl value of about 20 to 200 KOH mg/g, preferablyabout 25 to 80 KOH mg/g; a softening point of about 50 to 150° C.,preferably about 70 to 140° C.; and a weight-average molecular weight ofabout 1,000 to 10,000, preferably about 2,000 to 5,000. Typical examplesof the hydroxyl group-containing polyester resins are those obtained byreacting an aromatic or alicyclic dicarboxylic acids such as phthalicacid (or its anhydride), isophthalic acid, terephthalic acid, dimethylisophthalate, dimethyl terephthalate, hexahydrophthalic acid (or itsanhydride), tetrahydrophthalic acid (or its anhydride), or the like; anda bivalent alcohols such as (poly)ethylene glycol, (poly)propyleneglycol, butylene glycol, neopentyl glycol, 1,6-hexanediol,dimethylpropionic acid or the like; and additionally if desired, amonocarboxylic acid such as benzoic acid or the like; a trivalent orhigher-valent carboxylic acid such as trimellitic acid (or itsanhydride) or the like; and a trivalent or higher-valent alcohol such astrimethylolethane, trimethyrolpropane, glycerin, pentaerythritol, or thelike; so that the resins have a hydroxyl value in the range describedabove.

The blocked polyisocyanate compounds are, for example, those obtained byblocking the isocyanate groups in an aliphatic or alicyclicpolyisocyanate compound such as trimethylene diisocyanate, isophronediisocyanate, hydrogenated xylylene diisocyanate, or the like, with acompound such as phenols, lactams, alcohols, oximes or the like. Thecompound obtained by blocking all isocyanate groups in isophronediisocyanate so that there is no free isocyanate group left with alactam-derived blocking agent such as ε-caprolactam or the like isparticularly preferred.

(v) Combination of a Carboxyl Group-Containing Polyester Resin and aHydroxyalkylamide Compound

The carboxyl group-containing polyester resins to be used are preferablythose having a resin acid value of 20 to 200 KOH mg/g, preferably about25 to 150 KOH mg/g; a softening point of about 50 to 150° C., preferablyabout 70 to 140° C.; and a weight-average molecular weight of about1,000 to 10,000, preferably about 2,000 to 5,000. Typical examples ofthe carboxyl group-containing polyester resins are those obtained byreacting an aforedescribed aromatic or alicyclic dicarboxylic acid andan aforedescribed bivalent alcohol, and additionally if desired, amonocarboxylic acid such as benzoic acid or the like; a trivalent orhigher-valent carboxylic acid (or its anhydride) such as trimelliticacid or the like; and a trivalent or higher-valent alcohol such astrimethylolethane, trimethyrolpropane, glycerin, pentaerythritol or thelike; so that the resins have an acid value in the range describedabove.

(vi) Combination of a Carboxyl Group-Containing Polyester Resin and anEpoxy Resin

The carboxyl group-containing polyester resins to be use are, forexample, those similar to resins (v) above. The epoxy resins havepreferably an epoxy equivalence of 200 to 3,000, preferably 300 to2,000; and a softening point of about 20 to 200° C., preferably about 30to 150° C. Typical examples of the epoxy resins include bisphenol A-typeepoxy resins, bisphenol F-type epoxy resins, bisphenol B-type epoxyresins, acrylic epoxy resins, brominated epoxy resins, cyclic aliphaticepoxy resins (epoxy resins having cylcohexene oxide groups,tricyclodecene oxide groups, cyclopentene oxide groups or the like), andthe like. From the viewpoint of hardenability, among the resins above,bisphenol A—epichlorohydrin-type epoxy resins are particularlypreferable, and specific examples thereof include AER-6014 (brand nameof Asahi Kasei Corp.), Epikote 1004, Epikote 1007 (hitherto, brand namesof Japan Epoxy Resins Co., Ltd), Araldite 6084, Araldite 6097, Araldite6099 (hitherto, brand names of Ciba-Geigy Corp.), DER-664, DER-667(hitherto, brand names of Dow Chemical Com.), and the like.

(vii) Combination of an Epoxy Group-Containing Acrylic Resin and aPolycarboxylic Acid Compound

The epoxy group-containing acrylic resins to be used are preferablythose having an epoxy equivalence of 200 to 3,000, preferably 300 to2,000; and a softening point of about 20 to 200° C., preferably about 30to 150° C. Typical examples of the epoxy group-containing acrylic resinsare epoxy group-containing acrylic resins obtained by radicalcopolymerization reactions of an epoxy group-containing radicallypolymerizable unsaturated monomer (e.g., glycidyl(meth)acrylate,methylglycidyl meth)acrylate, or the like) as an essential monomeringredient with, for example, methyl methacrylate, ethyl methacrylate,isobutyl methacrylate, tert-butyl methacrylate, tert-butyl acrylate,methyl acrylate, ethyl acrylate, n-butyl methacrylate, isobutylacrylate, 2-ethylhexyl (meth)acrylate, stearyl methacrylate, styrene,vinyltoluene, α-methylstyrene, (meth)acrylonitrile, (meth)acrylamide,hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate or the like.

The polycarboxylic acid compounds are, for example, dodecanedicarboxylicacid, decanedicarboxylic acid, adipic acid, sebacic acid and the like.

(viii) Combination of a Hydroxyl Group-Containing Acrylic Resin and aBlocked Polyisocyanate Compound

The hydroxyl group-containing acrylic resins to be used are preferablythose having a hydroxyl value of about 20 to 200 KOH mg/g, preferablyabout 25 to 80 KOH mg/g; a softening point of about 50 to 150° C.,preferably about 70 to 140° C.; and a weight-average molecular weight ofabout 1,000 to 100,000, preferably about 2,000 to 80,000. Examples ofthe hydroxyl group-containing acrylic resins include those obtained byradical copolymerization reactions of a hydroxyl group-containingradically polymerizable unsaturated monomer such as above-describedhydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate or the like asan essential monomer ingredient, with another monomer other than thehydroxyl group-containing radically polymerizable unsaturated monomer(e.g., monomers described as the constituent of the aforementioned epoxygroup-containing acrylic resins). The blocked polyisocyanate compoundsexemplified in (iv) above can be used.

The “coloring pigments” to be used in the paint powders are, forexample, inorganic or organic coloring pigments such as titaniumdioxide, iron oxide, iron oxide red, carbon black, phthalocyanine blue,phthalocyanine green, quinacridone pigments, isoindolinone pigments, azopigments, Acetron pigments, various calcined pigments, and the like. The“extender pigments” to be added in the paint powders are, for example,calcium carbonate, glass fiber, silica, talc, sulfuric acid barium,kaolin, and the like. In addition, anti-corrosive pigments such as zincpowder, aluminum dihydrogen tripolyphosphate, and the like may also beused if desired. These pigments are listed here only as examples and itshould be understood that the coloring pigments of the present inventionare not limited thereto.

The “additives” include, for example, surface modifiers, hardeningaccelerators, anti-sagging agents, UV absorbents, photostabilizers,antioxidants, dyes, and the like, and may be additionally used ifdesired.

The paint compositions thus prepared containing the resins above andadditionally the coloring pigments, additives and the like if desiredare then kneaded into homogeneity at the temperature of the resin beingmelted. The paint pellets obtained are pulverized and then screened togive base paint powders having an average diameter of about 10 to 100μm, preferably 20 to 60 μm.

In the present invention, the “average diameter” means the particle sizeat the integrated value of 50% from the smallest particle size (D₅₀)when the particle size distribution of the base paint powders or pigmentparticles after screening is determined by a common particle sizedistribution analyzer. The particle size distribution can be determinedby analyzing the strength and pattern of diffracted and scattered lightwhen light is irradiated to particles. It is because the strength andpattern of the diffracted and scattered light depends on the size of theparticles. Examples of the particle size distribution analyzers areMicrotrac 9220 FRA and Microtrac HRA of Nikkiso Co., Ltd; CoulterMurtisizer of Beckmann Coulter, Inc.; and the like. In a typical exampleof the measurement method, the particle size distribution is determinedby the following way: into a container containing a well stirredsolution of 0.01 to 0.1 g of a neutral detergent in 30 ml of water,added is 0.01 to 0.2 g of a sample; the suspension is dispersed for 2minutes under ultrasonic irradiation while stirring; and the particlesize distribution is measured by one of the particle size distributionanalyzers above.

Next, the “pigment particles” according to the present invention will bedescribed.

The “pigments” to be used as the “pigment particles” according to thepresent invention are mainly “bright pigments”, “phosphorescentpigments” and “coloring pigments”. Among them, the “bright pigments” arenot particularly limited if they provide coated films withattractiveness of appearance such as metallic and pearl appearance(light interference pattern) and the like by reflecting the incominglight, and are preferably, for example, one or multiple pigmentsselected from the groups consisting of metal powders such as aluminumpowder and the like; and metal flakes such as stainless steel flakes andthe like; pearl pigments such as mica, micaceous iron oxide (MIO,flake-like iron oxide), glass flakes, pearl mica and the like. Inaddition, coated products of the pigments exemplified above, such asresin-coated aluminum powders, silica-coated aluminum powders, fluorinecompound-coated aluminum powders, titanium-coated mica, Hastelloy-coatedglass flakes, and the like, are also included in the bright pigments ofthe invention.

The “phosphorescent pigments” are pigments having the property ofabsorbing visible, ultraviolet, and other light and emitting lightwithout generating heat. The “phosphorescent pigments” are, for example,zinc sulfide, strontium aluminate, calcium aluminate, barium aluminate,magnesium aluminate, and the like, and may additionally containeuropium, dysprosium, neodymium, and the like blended as an activator.In the present invention, the phosphorescent pigments may be used aloneor in combination of two or more, and are not limited thereto.

The “coloring pigments” are pigments used primarily for the purpose ofproviding coated film with hue and attractiveness of appearance. The“coloring pigments” are often contained in the “base paint powders”, butthe separate addition and bonding of the coloring pigments onto thesurface of the “base paint powders” via shellac is sometimes moreeffective in increasing attractiveness of the appearance of theresulting coated films than the blending of coloring pigments only tobase paint powder. The “coloring pigments” includes pigments similar tothose exemplified above; may be used alone of in combination of two ormore; and are not limited to the examples above.

The “shellac” according to the present invention is a naturalthermosetting resin purified from the secretion of scale insects(mainly, lac insects) living on leguminous plants (lebbek, guango,Acacia caatechu, pigeon pea, babul, and the like) or mulberry plants(bunyan, pipal, and the like). The shellac is soluble in lower alcohols(mainly, monovalent C₁-C₄ alcohols) at room temperature, and onceheat-hardened, scarcely soluble in not only major organic solvents andaqueous solvents excluding warm alkaline water but also in loweralcohols, and thus it is extremely suitable as a paint ingredient.

The “shellacs” include commercially available white shellacs that aredecolored and dewaxed shellacs, and any of these shellacs may be used inthe present invention without limitation. The shellac, although thechemical structure thereof is not completely clear, mainly consists ofpolyesters having at least aleuritic acid and shellolic acid describedbelow and the derivatives thereof as the constituents, and the hydroxylgroups present in the structures thereof are likely the reason forshellac exhibiting a favorable property in the powder paints of thepresent invention. In addition, the presence of butolic acid, palmiticacid, myristic acid, and the like is also confirmed in shellac.Accordingly, the “shellac” according to the present invention includesnot only natural shellacs but also synthetic resins prepared based onthe estimated chemical structure, having the same operation and effectas that described above.

The content of the “shellac” with respect to the total amount of powderpaint is preferably 0.01 to 1 mass %. The presence of shellac in theamount of less than 0.01 mass % can make it more difficult to bind thepigment particles and the base paint powders uniformly, while thepresence thereof of more than 1 mass % can affect the evenness of thecoated surfaces.

The average diameter of the “base paint powders” is preferably 10 to 100μm. Base paint powders with an average diameter of less than 10 μm havea larger repose angle and can be thus poorer in flowablility, reducingcoating efficiency, while those of over 100 μm can lead to decrease incoating efficiency, for example, by detachment of the paints from thesurface of substrates during coating. The “repose angle” is an angle ofthe slope of the mound that is formed when the powder paints are pouredonto a circular plate, and may be determined by, for example, PowderTester (brand name, Hosokawa Micron Corp.).

The average diameter of the “pigment particles” is preferably not morethan 100 μm. With the value of over 100 μm, the pigment particles becomemore resistant to uniform binding to the base powder paints, leading toincrease in the number of pigment particles detached and to decrease inthe attractiveness of appearance of coated surfaces.

When bright pigments are used as the pigment particles, the brightpigments have preferably an average diameter of 2 μm or more, and 100 μmor less, more preferably 3 μm or more, and 80 μm or less. In addition,the favorable thickness thereof is 0.01 μm or more, and 10 μm or less,more preferably 0.1 μm or more, and 6 μm or less. More specifically, inthe case of aluminum flakes, the flakes preferably have an averagediameter of 2 μm or more, and 50 μm or less, and a thickness of 0.2 μmor more, and 5 μm or less; and in the case of pearl pigments, thepigments preferably have an average diameter of 5 μm or more, and 70 μmor less, and a thickness of 0.2 μm or more, and 5 μm or less.

Alternatively, when inorganic coloring pigments are used as the pigmentparticles, the pigments preferably have an average diameter of 0.01 μmor more, and 5.0 μm or less; while when organic coloring pigments areused, the pigments preferably have an average diameter of 0.01 μm ormore, and 1.0 μm or less. In the case of phosphorescent pigments, thepigments preferably have an average diameter of 1 μm or more, and 100 μmor less, particularly preferably 5 μm or more, and 50 μm or less.

The content of the “pigment particles” is preferably 0.1 to 50 mass %with respect to the total amount of powder paints. With the pigmentparticles in an amount of less than 0.1 mass %, the amount of pigmentparticles in the paint can be not sufficient, sometimes resulting incoated films less attractive in appearance. Alternatively, with thepigment in an amount of over 50 mass %, the amount of the pigmentparticles is too excessive with respect to the base paint powders,leading to increase in the number of pigment particles that are notbound to the base paint powders and present independently and todecrease in attractiveness of appearance, as the coated films becomesimilar to those obtained by the base powder paints prepared simply bydry blending. The amount is more preferably 0.5 mass % or more, and 40mass % or less.

The powder paints of the present invention may also contain otheradditives according to the need and applications. Such additivesinclude, for example, additives for increasing paint flowablility suchas silica particles, aluminum oxide, and the like. In addition, powderpaints containing other unavoidable impurities are also included in thescope of the present invention.

In producing the powder paints of the present invention, the processincludes at least a “step of blending the base paint powder and thepigment particle”, a “step of blending the resulting mixture with aliquid bonding auxiliary agent wherein shellac is dissolved in anorganic solvent” and a “step of drying”, and these steps should beoperated in that order.

Accordingly, it is necessary first to blend the paint ingredients,especially the base paint powder and pigment particle, significantlywell for producing the powder paint of the present invention.Insufficient blending thereof often causes maldistribution of the basepaint powders or pigment particles, and increases the possibility of thesame base paint powders or pigment particles binding to each other, thusmaking it difficult to produce coated films more attractive inappearance.

The blending method is not particularly limited if the paint ingredientscan be sufficiently blended, and the blending is commonly conducted byusing a mechanically agitating blender or an airstream fluidizedblender.

The “mechanically agitating blender” is, for example, a mechanicallyagitating blender driven by a hanging shaft. As shown in FIG. 1, themechanically agitating blender driven by a hanging shaft is equippedwith an agitator shaft 2 and a motor 3 driving the same in a reverseconical housing 1, and has an exhaust opening 4 for discharging thepaint powders after blending. The number, 2 a, represents the blendingblades connected to the agitator shaft.

The mixing condition in the “mechanically agitating blender” is acondition under which the base paint powders, pigment particles, and thelike are uniformly blended and the pigment particles are not brokendown. It is because the damage of the bright pigments leads to reductionin the attractiveness of appearance, particularly when bright pigmentsare used as the “pigment particles”. The rotational velocity of theagitating blender satisfying the condition above is preferably aperipheral velocity of 3 to 6 m/s. The rotational velocity slower thanthat described above makes it difficult to conduct sufficiently uniformblending, and alternatively, the rotational velocity faster than thatleads to breakdown of the pigment particles due to the shearing force ofthe agitating blades.

When blended at the peripheral velocity of 3 to 6 m/s in the hangingshaft driving-type mechanically agitating blender, the particles,especially high density bright pigments, tend to stay in the dead spacelocated at the vicinity of the bottom of container 1 (indicated by “d”in FIG. 1) and may not be dispersed well. Therefore, it is preferable tostir the particles while supplying air into the space between theagitating shaft and the bottom of container 1 for more uniform blending.

FIG. 2 shows a schematic illustration of an “airstream fluidizedblender”. In FIG. 2, the ingredients such as base paint powders and thelike present in chamber 6 are uniformly dispersed and blended in chamber6 by the airstream supplied from airstream generation equipment 7through airstream generator hole 9. This airstream fluidized blenderdoes not damage the pigment particles and others, and thus is favorableas it allows production of coated films attractive in appearance.

In the process of producing powder paints according to the presentinvention, a base paint powder and a pigment particle are first blendeduniformly, and subsequently a liquid bonding auxiliary agent whereinshellac is dissolved in an organic solvent is blended to the base paintand pigment powder mixture uniformly.

The “organic solvent” to be used is not particularly limited if it candissolve shellac and hardly dissolve the resins contained in the powderpaint, and are, for example, those having as the main components one ormultiple mixed solvents of monovalent alcohols selected from methanol,ethanol, n-propanol, isopropanol, butanol, and the like. In addition,the organic solvent may contain, in addition to the monovalent alcoholabove, polyvalent alcohols such as ethylene glycol and the like; esterssuch as methyl acetate, butyl acetate, and the like; ketones such asmethylethylketone and the like; ethers such as dimethylether,methylethylether, and the like; aromatic hydrocarbons such as benzene,xylene, and the like; and aliphatic hydrocarbons such as hexane,heptane, and the like.

In the present invention, a solution of shellac in the organic solventdescribed above is added as the “liquid bonding auxiliary agent”, andsmaller droplets thereof during the addition leads to production of thepaint more attractive in appearance. What is first discovered by thepresent inventors is that the droplets of the liquid bonding auxiliaryagent having a diameter of 1 mm or less suppress the binding of the samebase paint or pigment powders to each other even though the reason isnot clear, and thus allow more uniform binding between the base paintand pigment particles. In addition, such droplets somehow provide thepowder paint with resistance against the blocking of the ingredientsduring the storage thereof. The term, “blocking”, means phenomenawherein the paint powders adhere to each other, forming rice-grain sizedclumps or solidify the entire paint powders in the container to such anextent that it is difficult to bring the solidified paint powders backto the original paint powders with slight force. As these advantageouseffects increase when the droplets become even smaller, the dropletspreferably have a diameter of 100 μm or less, more preferably 50 μm orless. Smaller droplets also have an additional advantage in allowingeasier and uniform blending of the liquid bonding auxiliary agent withthe base paint powders and pigment particles.

By the operation and effect of the “liquid bonding auxiliary agent”, thebond between the base paint powders and pigment particles issignificantly strengthened, eliminating the problem of separationthereof during the coating operation and the like.

The “liquid bonding auxiliary agent” should adhere to both base paintpowders and pigment particles uniformly. Uneven adhesion leads todeviation in the bonding strength between the base paint powders and thepigment particles, and affects the attractiveness of appearance of thecoated films. In order to attain uniform adhesion, it is preferable toadd the liquid bonding auxiliary agent by spraying or dropwise addition,more preferably by spraying. It is because the liquid bonding auxiliaryagent can be uniformly adhered more easily by spraying.

When the ingredients are mixed by a mechanically agitating blender, theliquid bonding auxiliary agent may be added either by spraying ordropwise addition. For example in FIG. 1, a liquid bonding auxiliaryagent can be blended uniformly by adding the liquid bonding auxiliaryagent by spraying or dropwise addition via injection port 5 while mixingthe ingredients. Although only one injection port 5 for adding theliquid bonding auxiliary agent is set forth in FIG. 1, multipleinjection ports may be placed in order to add the liquid bondingauxiliary agent more uniformly.

Alternatively when an airstream fluidized blender is used, it ispreferable to add liquid bonding auxiliary agent by spraying. That is,spraying the liquid bonding auxiliary agent c via bonding auxiliaryagent-injection port 8 in FIG. 2 to the ingredients homogeneouslydispersed in chamber 6 allows uniform blending of the bonding auxiliaryagent all over the constituents. Similarly, multiple bonding auxiliaryagent-injection ports 8 may be placed as in the mechanically agitatingblenders.

The amount of the “liquid bonding auxiliary agent” added is preferably 1to 100 mass % with respect to the amount of the entire powder paintexcluding shellac, i.e., the total amount of the “base paint powders”,“pigment particles”, and “others additives”. The amount of less than 1mass % sometimes leads to insufficient bonding between the base paintpowders and the pigment particles, while the amount over 100 mass % maylead to elongation of the period required for addition and drying andthus decrease in productivity. As for the concentration of shellac inthe liquid bonding auxiliary agent, a favorable concentration calculatedfrom the amount of shellac to be included in the powder paint and theamount of the liquid bonding auxiliary agent to be added may be adopted.

The process of producing powder paints according to the presentinvention includes a drying step. The drying step is conducted forevaporating the organic solvent in the liquid bonding auxiliary agentand the like and for ensuring firm bonding between the base paintpowders and the pigment particles.

The means for drying is not particularly limited, but is for examplesupplying air. And considering the operating efficiency, the air ispreferably heated. The temperature of the air may be determinedappropriately, but should be at least lower than the softening points ofthe powder paint resin ingredients. When the temperature is higher thanthe softening points, the resins soften and cause the blocking of thepowder particles. The “softening point” of the present invention can bedetermined, for example, by placing a sample in a hot glycerin bathheated at a programmed temperature increase rate of 3° C./min, anddetermining the temperature at which the sample softens and falls byusing a automatic ring and ball softening point tester (MEITECH company,Ltd).

The temperature of the drying air is generally 20 to 120° C., morepreferably 40 to 100° C. Further, the period of supplying the air mayalso be decided arbitrarily; for example, the ingredients may be heatedby supplying the heated air after addition of the liquid bondingauxiliary agent and then cooled; or the constituents may be heated bysupplying the heated air while the liquid bonding auxiliary agent beingadded and then cooled.

When a mechanically agitating blender is employed for blending, the airis supplied into the space between the bottom of container 1 and theblending shaft in FIG. 1, in a similar manner to the mode for blendingthe base paint powders and the pigment particles uniformly.

When an airstream fluidized blender is employed for blending, theairstream per se has a drying capability, and when heated air issupplied as the airstream, the drying efficiency will become evenhigher.

The powder paints produced in this way can be coated on substrates byelectrostatic coating, fluidized-bed coating, spraying, in-mold or othercoating methods, and baked in a hot-air oven, infrared oven, inductionheating oven or the like to give hardened coated films. As the basepaint powders and the pigment particles are firmly bound to each otherin the powder paints according to the present invention, theseingredients do not separate even during coating by the electrostaticcoating method, preventing adhesion thereof to the coating machine,especially to the tip portions of the coating machine, and allowingstable coating operation.

The process of producing coated products according to the presentinvention comprises a step of coating the abovementioned powder paintonto the substrate made of metal material by electrostatic powdercoating. In the process of producing coated products, the base paintpowders and the pigment particles do not easily separate. And especiallywhen a metallic metal pigment is used as the pigment particle, themetallic metal pigment, for example, flake-like metal flakes or thelike, blended in the powder paint are oriented uniformly in the coatedfilms; and thus the process provides the coated films fewer in dullness,more attractive in appearance, and having smaller difference in metallicappearance when viewed from front and in the direction differenttherefrom and fewer black spots due to the absence of metallic metalpigments. Similarly when a flake-like pearl mica is used as the pigmentparticle, the process of the invention provides coated films havingsmaller difference in peral-like appearance when viewed from front andin the direction different therefrom and a smaller number of decoloredspots (transparent, revealing the substrate) due to the absence of thepearl pigments, without deterioration in the pearl-like appearance ofthe entire coated film.

In the process of the present invention, metal materials are used as thesubstrates. It is for the purpose of revealing the difference betweenthe inventive and conventional processes more distinctly. It is becausewhile the use of conventional powder paints in the electrostatic powdercoating, which is suitable for coating of metallic substrates, mayreduce attractiveness of appearance of the coated films, the use of thepowder paints of the present invention eliminates such a concern. Thekind of the metal materials is not particularly limited, and examplesthereof include most widely used ferrous metal materials such as steel,alloy steel, and the like; nonferrous metal materials such as aluminum,stainless, zinc, tin, copper, titanium, magnesium, brass, and the like,and alloys thereof; plated metal materials such as galvanized steelplates, tinned steel plates, and the like; surface-treated metalmaterials such as those chemically treated with chromic acid orphosphate salt-based, titanium-based, zirconium-based, organic metalsalt-based, and other non-chromium-based reagents; and aluminum metalmaterials and alloys that are previously subjected to anodic oxidation,sealing, and the like.

The substrates made of the metal materials above may be those thatprovide directly final products after the coating step, but include anykinds of substrates that require coating, for example, those providingcomponents of final products or semi-processed products. The phrase, thesubstrates “made of metal material”, means a substrate wherein thesurface thereof to be coated is mainly made of metal material, andaccordingly the substrates include those having non-metal materials,such as resins and the like, on some part of the surface or in otherinternal portions.

The thickness of coated films formed by the process of the presentinvention is usually 30 to 250 μm, preferably 60 to 150 μm, afterbaking. The coated films having a thickness of less than 30 μm tend tobecome lower in evenness and also have nonconformity in appearance, dueto distinguishable seediness of the surface. Alternatively, the coatedfilms having a film thickness of over 250 μm, tend to have problems ofgeneration of solvent poppings, rough surface due to electrostaticrepulsion, and the like.

The powder paints are baked under a condition of the surface temperatureof metal materials at 130 to 350° C., preferably 140 to 250° C., for 30seconds to 60 minutes, preferably 1 to 50 minutes.

When the metal materials have casting surface, or when the appearance ofthe finished products can be damaged by the irregularity of thesubstrate surface, it is useful to have, after degreasing and chemicallytreating the metal substrates, the combination of a step of forming aprimer layer made of the powder paints and a step of coating theappearance-improving powder paints over the primer layer, for thepurpose of ensuring the attractiveness of appearance by suppressing theirregularity of the raw materials, and providing further improvedadhesiveness and corrosion resistance.

The primer layer may also be formed for other purposes than thosedescribed above, for example, for production of the metal components tobe used under harsh conditions. When a colored coated film is formed asthe primer layer, it is possible to provide the coated films withstereoscopic effect, depth, unique pattern, and the like, as well as theattractiveness of appearance such as metallic and pearl appearance, andthus to further increase the attractiveness of appearance of coatedfilm, by properly selecting a hue of the primer layer different fromthat of the coated film formed with the paint powder according to thepresent invention. The primer layer may be formed of course with thepaint powders according to the present invention.

As the primer compositions for forming the primer layers, any resincompositions commonly used in the paint industry may used withoutparticular limitation, and the composition may be selected properlyaccording to the kind of metal substrates, and the shape, application,requirements, or the like of the substrates. Typical examples of theresins constituting the primer composition include epoxy resin primers,acrylic resin primers, polyester resin primers, epoxy polyester resinprimers, and the like. These primer compositions may be in any of thefollowing types: heat hardening-type, normal temperature hardening type,or lacquer type. The primer compositions may also be in any of thestates: organic solution (including high solid content systems having asolid content of 40 mass % or more), aqueous solution, and powder.

In forming the primer layer with powder paints, various thermosettingresins may be used as the base paint powders of the primer powderpaints, but it is preferable to use resins similar to the base resins ofthe paint powders of this invention for the coated films, which are tobe formed over the primer layer. The use of similar resins ensures highadhesiveness between the two layers and prevention of the defects inappearance such as cissing, cratering, and the like due to the dusts ofdifferent paints For example, a polyester resin is preferable when apolyester resin is used as the film-forming resin in the base paintpowder, while an acrylic resin, when an acrylic resin is used as thefilm-forming resin in the base paint powder. Further, it is preferableto use a resin that can make the final products more anti-corrosive bycoating the metal substrates.

More specifically, when the film-forming resin of the base paint powderis a β-hydroxyalkylamide hardening-type polyester resin, a paint powderhaving an epoxy hardening-type polyester resin as the base paint powderis preferably used for the primer layer. The epoxy hardening-typepolyester resin paint powders include, for example, Everclad No. 2100produced by Kansai Paint Co., Ltd, which is favorable from the viewpointof performance of coated films and cost effectiveness.

Alternatively, when the base paint powder is constituted with aβ-hydroxyalkylamide hardening-type acrylic resin, a paint powder havinga dodecanedicarboxylic acid hardening-type epoxy group-containingacrylic resin as the base paint is preferably used as the primer layer.The dodecanedicarboxylic acid hardening-type epoxy group-containingacrylic resin paint powders include, for example, Everclad No. 5600DKproduced by Kansai Paint Co., Ltd, which is favorable from the viewpointof performance of coated films and attractiveness of appearance.

The powder paints for forming the primer layers may contain coloringpigments, extender pigments, anti-corrosive pigments, and the like, andmay be those without pigments for producing transparent coated films. Ifthe heat flowablility of the primer layer paints is greater than that ofthe powder paints according to the present invention for forming coatedfilms over the primer layer, the finished appearance of the coatedproducts will be further improved.

In the step of forming primer layers, the powder primers may be baked tocomplete hardening after coating; or slightly pre-heated to such anextent that the powder particles are thermally fused mildly; or onlycoated without any heat treatment and baked simultaneously with thecoated films after application of the powder paint of the presentinvention.

If the primer layer is baked to complete hardening, the thickness of theprimer layer is preferably 30 to 250 μm, preferably 60 to 150 μm, andthe layer is baked at a constant temperature of 130 to 350° C.,preferably 140 to 250° C. for 30 seconds to 60 minutes (preferably, 1 to50 minutes). Alternatively, if the primer layer is partially heat-fusedas described above or simply coated without any heating and then thepowder paint of the present invention is coated, it is possible toreduce the thickness of the resulting coated layers respectively by 40to 60% from those in the case where the layers are formed and bakedindependently. When two different layers of paints are piled and bakedsimultaneously, the appearance-improving powder paints, even with a filmthickness 40 to 60% thinner than the thickness required for the filmswhich are produced by coating the paint powders alone, provide coatedfilms excellent in evenness and attractiveness of appearance, as thepaint powders exhibit favorable heat-flowablility together with theprimer layer.

In the process of producing coated films of the present invention, it ispossible to add a step of forming a top clear layer over the coatedfilms prepared by the powder paints of the present invention, whichleads to further increase in the performance of coated films, forexample, in weatherability, attractiveness in finished appearance suchas high brilliance, scuff resistance, and chemical resistance, etc. Thestep of forming the top clear layer may be conducted regardless of thepresence or absence of the primer layer formed.

The top clear layer is preferably formed with an acrylic clear paint.Such acrylic clear paints include, for example, acrylic solvent-basedclear paints (e.g., ALC-100 Clear of Kansai Paint Co., Ltd) which arecommonly used as top-coats of auto body and parts; acrylic solvent-basedhigh solid-content clear paints (preferably, having a solid content of40 mass % or more); two-component polyisocyanate hardening-type acrylicclear paints (e.g., Super Diamond Clear Q of Kansai Paint); and acrylicpowder paints (e.g., Everclad No. 5600DK of Kansai Paint Co., Ltd).Incidentally, Everclad No. 5600DK, an acrylic powder paint of KansaiPaint Co., Ltd, exhibits an excellent performance also as a primer layerpaint, a good adhesiveness to various metal materials, and an excellentcorrosion resistance.

The film-forming resins to be used for the acrylic solvent-based clearpaints, which are used for forming the top clear layers, are generallymelamine hardening-type hydroxyl group-containing acrylic resins, andusually coated by spray coating.

The top clear layers are baked by keeping the layers at a temperature of120 to 160° C. for 10 to 40 minutes. The thickness thereof after dryingis preferably 20 to 50 μm.

When a solvent-type clear paint of the two-component polyisocyanatehardening-type hydroxyl group-containing acrylic resin is used for thetop clear layer, the paint can be baked at a lower temperature of as lowas 60 to 80° C. In such a case, the paint is coated by spray coating tosuch a degree that the film thickness after drying becomes 20 to 50 μm.

When a dodecanedicarboxylic acid hardening-type epoxy group-containingacrylic resin powder paint (e.g., Everclad No. 5600DK of Kansai PaintCo., Ltd) is used for forming the top clear layer, it is preferable thatthe primer layer is also formed with a powder paint; that is, all coatedfilm layers are formed with powder paints. In such a way, coated filmscan be formed without any adverse effect of volatile organic substancesincluding harmful organic solvents on humans and the environment, as theemission thereof can be almost eliminated. In addition, as it ispossible to recover and reuse all paints including the powder paints ofthe present invention, the use of only powder paints is advantageous init high reuse efficiency and cost effective.

The kinds of coated products obtainable by the process described aboveare not particularly limited, and examples thereof include automobilematerials (body, auto parts (including aluminum wheel, iron wheel,stainless wheel, magnesium alloy wheel, and the like)), buildingmaterials, containers (such as gas containers), trains, ships, vehicles,consumer electronics, office machines, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a hanging shaft driving-typemechanically agitating blender.

FIG. 2 is a schematic illustration of an airstream fluidized blender.

FIG. 3 shows a macrophotograph of paint particles in the powder paintprepared by the production process according to the present invention.

FIG. 4 shows a macrophotograph of paint particles in the powder paintprepared by dry blending method (conventional method).

FIG. 5 shows a macrophotograph of a coated film prepared with a powderpaint by the production process of the present invention.

FIG. 6 shows a macrophotograph of a coated film prepared with a powderpaint by dry blending method (conventional method).

EXAMPLES

Hereinafter, the present invention will be described in more detail withreference to Examples and Test Examples, but it should be understoodthat the scope of the present invention is not limited thereto.

Production Example 1

Production of Base Paint Powders

The compounds set forth in Table 1 were blended in the composition setforth in Table 1 (respectively, expressed in relative amounts), andmelt-kneaded at the melt-kneading temperature set forth in Table 1 intopellet-type compositions A, B, C, D, and E for powder paints. TABLE 1Powder Paint Composition A B C D E Thermosetting polyester resin 1 80 —— — 80 Thermosetting polyester resin 2 —  95 — — — Thermosettingpolyester resin 3 — — 50 — — Thermosetting acrylic resin — — — 80 —Polyisocyanate compound 16 — — — 16 Hydroxyalkylamide —  5 — — — Epoxyresin — — 46 — — Dodecanedicarboxylic acid — — — 18 — Titanium dioxide —— — — 45 Melt-kneading temperature (° C.) 130  130 110  90 130 

In Table 1, thermosetting polyester resin 1 used was “Finedic M-8050(brand name)” (hydroxyl value: 49 mg KOH/g) produced by Dainippon Inkand Chemicals, Inc. The polyisocyanate compound was “B-1530 (brandname)” (a polyisocyanate block copolymer from isophrone diisocyanate(IPDI) and ε-caprolactam) of Huls.

Thermosetting polyester resin 2 was “Finedic M-8961 (brand name)” (acidvalue: 33 mg KOH/g) of Dainippon Ink and Chemicals, Inc. Thehydroxyalkylamide was “XL-552 (brand name)” (β-hydroxyethyl adipamide,hydroxyl equivalence: 84) of EMS.

Thermosetting polyester resin 3 was “U-PiCA Coat GV-230 (brand name)”(acid value: 53 mg KOH/g) of Japan U-PiCA, Ltd. The epoxy resin was anepoxy resin of Asahi Kasei Corp., “AER-6014 (brand name)” (epoxyequivalence: 980).

The thermosetting acrylic resin was “Almatex PD3413 (brand name)” (epoxyequivalence 470) of Mitsui Chemicals, Inc. Titanium dioxide was “TitanixJR-605 (brand name)” of Tayca Corp.

Pelletized compositions A, B, C, and E for powder paints were pulverizedand screened through a 84 μm sieve respectively to give base paintpowders A, B, C, and E having an average diameter of 43 μm.Alternatively, pelletized powder paint composition D was pulverized andscreened through a 74 μm sieve to give base paint powder D having anaverage diameter of 35 μm.

Production Example 2

Production of Liquid Bonding Auxiliary Agents

The compounds set forth in Table 2 were blended in the composition setforth in Table 2 (respectively, expressed in relative amounts) andstirred in a disperser to give liquid bonding auxiliary agents a, b, c,d, e, and f. TABLE 2 Liquid Bonding Aid a b c d e f Shellac  2  2  2  20.09 20 Methanol 98 — 49 95  99.91 80 Isopropanol — 98 49 — — — Butylacetate — — — 3 — —

In Table 2, the shellac used was “Bleached Dewaxed Shellac (brand name)”produced by Japan Shellac Industries, Ltd.

Example 1

To each base paint powder, A to E, prepared in Production Example 1, analuminum pigment (“PCF-7670A” (brand name) of Toyo Aluminum K.K.) havingan average diameter of about 18 μm; a pearl pigment (“Iriodin 103 WNT”(brand name) of Merck Ltd., Japan) having an average diameter of about60 μm; a stainless steel flake (“Stainless Paste 01-1204” (brand name)of Toyo Aluminum K.K.) having an average diameter of about 60 μm; aphosphorescent pigment (“G-300F” (brand name) of Nemoto & Co., Ltd.)having an average diameter of about 10 μm; or a carbon black (“carbonblack MA-100” (brand name) of Mitsubishi Chemical Corp.) having anaverage diameter of about 24 nm; was added as a pigment particle. Theresulting mixtures were stirred and blended; added respectively with aliquid bonding auxiliary agent, a, b, c, d, e, or f, prepared inProduction Example 2 by spraying; and dried by supplying heated air at80° C. in an airstream fluidized blender, Agglomaster (brand name) ofHosokawa Micron Corp., giving powder paints Nos. 1 to 14 set forth inTable 3.

Separately as comparative examples, powder paints having the compositionof Nos. 15 and 16 in Table 3 were prepared by the dry blending method.These powder paints were prepared by using the Agglomaster (brand name)of Hosokawa Micron Corp. as a mixer/drier 5 in the similar manner toabove, except that the liquid bonding auxiliary agent was not added, andthat they were prepared simply by blending a base paint powder and analuminum pigment under supplied air at normal temperature. TABLE 3 No. 12 3 4 5 6 7 8 Paint powder: kind A A A A A B C D amount 100 100 100 100100 100 100 100 Aluminum pigment 5 — — — — 5 5 5 Pearl pigment — 5 — — —— — — Stainless steel flake — — 5 — — — — — Phosphorescent pigment — — —30 — — — — Carbon black — — — — 0.1 — — — Liquid bonding aid: kind a a aa a a a a amount 10 10 10 10 10 10 10 10 solid content 0.2 0.2 0.2 0.20.2 0.2 0.2 0.2 No. 9 10 11 12 13 14 15 16 Paint powder: kind E A A A AA A A amount 100 100 100 100 100 100 100 100 Aluminum pigment — 5 5 5 55 5 — Pearl pigment — — — — — — — — Stainless steel flake — — — — — — —— Phosphorescent pigment — — — — — — — 30 Carbon black 0.1 — — — — — — —Liquid bonding aid: kind a b c d e f — — amount 10 10 10 10 12 1 — —solid content 0.2 0.2 0.2 0.2 0.0108 0.2 — —

Example 1

SPCC steel plates having a dimension of 0.8×70×150 mm galvanized withzinc phosphate (“PB-3118M” (brand name), Nihon Parkerizing Co., Ltd.)were coated using an electrostatic powder coating machine (GX108 (brandname), Nihon Parkerizing Co., Ltd.) under the following condition:

-   -   Voltage applied: −70 kV    -   Main air pressure: 0.6 kgf/cm²    -   Pattern air pressure: 1.0 kgf/cm²    -   Distance between gun and plate: 200 mm    -   Film thickness: 60 to 80 μm

Evaluation Example 1

Coating Efficiency

The flow of powder paints during continuous coating was observedvisually. Continuous coating without generation of spits was designatedas “◯”; with few generation of spits, “Δ”; and with frequent generation,“X”.

Evaluation Example 2

Properties of Coated Films

(I) Evenness

The evenness of coated films was determined by visual examination, andclassified into three categories: “{circle around (o)}” when the filmhas extremely high evenness; “◯” when the film may be regarded as even:and “X” when the film lacks evenness.

(II) Dispersion of Pigments

The degree of dispersion of the pigments used in coated films wasdetermined by visual examination, and classified into three categories:“◯” when the pigments are uniformly dispersed; “Δ” when the pigments areslightly maldistributed; and “X” when the pigments are unevenlydistributed.

Evaluation Example 3

Performances of Coated Films

(III) Adhesiveness

100 pieces of square coated films having a dimension of 1 mm×1 mm wereprepared by crosscutting coated films to the depth of substrate plateusing a cutter knife. An adhesive tape was applied onto the surface ofthe square coated films, and torn off violently at 23° C. The number ofthe square coated films remaining intact was determined by visualinspection, and the adhesiveness was designated as “◯” when the numberabove is 100.

(IV) Water Resistance

Coated films were immersed in hot water at 40° C. for 240 hours, andwere examined visually immediately after the coated films were pickedup. The water resistance was designated as “◯” when the coated films donot have any blisters, dulling, or other abnormalities. After drying ata temperature of 23° C. and a relative humidity of 50% for 2 hours, theadhesiveness of the films was determined in a similar manner to theadhesiveness test described above.

Evaluation Example 4

Possibility of Recovery and Reuse

The powder paints that were not adhered to the substrate plates in thetests for the coating efficiency (Evaluation Example 1), properties ofcoated films (Evaluation Example 2) and performances of coated films(Evaluation Example 3) above were recovered and reused for coating onceagain. And the dispersion of pigments in the coated films obtained wasanalyzed by visual examination. The possibility of recovery and reusewas designated as “◯” when the dispersion of the coated films isequivalent to that of the original coated films, and as “X” whenpigments are unevenly distributed.

Evaluation Example 5

Brightness

The brightness (metallic appearance) and unevenness in brightness(maldistribution of bright pigments) of coated films were evaluated byvisual examination, and was designated as “◯” when the brightness isgood and there is no unevenness in brightness; “Δ” when there is someunevenness and the brightness is lower; and “X” when there is unevennessin brightness all over the surface of the coated films and thebrightness is almost none.

Evaluation Example 6

Alkali Resistance

0.5 ml of 0.1 N aqueous sodium hydroxide solution was poured dropwiseonto coated films, and the films were left to stand at 50° C. for 3hours, washed with running water, and dried at a relative humidity of50% for 2 hours. Then, the surfaces of the films previously covered withthe droplets were examined by visual examination. The alkali resistancewas designated as “{circle around (o)}” when there is no abnormality atall; “◯” when there are some traces of the droplets observable butcausing no practical problems, “Δ” when the surface is slightlyblackened; and “X” when the surface is distinctly blackened.

Result 1

About Powder Paint Particles

FIG. 3 shows a macrophotograph of a powder paint particle (No. 1)according to the present invention, while FIG. 4 shows a macrophotographof another powder paint particle (No. 15) prepared by the dry blendingmethod.

In FIG. 3, it is observable that bright pigments are bound on thesurface of base paint powders.

While FIG. 4 indicates that the bright pigments are placed on but notbound to the surface of the base paint powders and there are somepigment particles fallen from the base paint powders and presentindependently. Such paint powders will not provide coated filmsattractive in appearance due to maldistribution of paint ingredientsduring coating, or will not allow recovery and reuse of the powderpaints as the pigment particles easily separate from the base paintpowders.

In contrast, the powder paints according to the present invention do notcause such problems, as the pigment particles are firmly bound to thebase paint powders via shellac. This result will be further verified bythe results in the Evaluation Example described below.

Result 2

Attractiveness of Appearance of Coated Surfaces

FIG. 5 shows a macrophotograph of a coated film prepared from powderpaint particle No. 1 according to the present invention, and FIG. 6 amacrophotograph of a coated film prepared from powder paint particle No.15 prepared by the conventional dry blending method.

In FIG. 6, there are several black spots observable here and there dueto the absence of bright pigments (aluminum pigments), which lead to asomber impression of the entire coated film.

In contrast, in FIG. 5, the bright pigments (aluminum pigments) arepresent all over the coated film; the black spots are smaller indiameter; and all paint ingredients are finely dispersed respectively,allowing uniform reflection of light from all over the surface and thusproviding the coated surfaces with a brilliantly shining beautifulappearance.

Result 3

Evaluation Results

The coating efficiency, properties of coated films, performances ofcoated films, and possibility of recovery and reuse of the powder paintsprepared in the Examples above were evaluated according to theevaluation methods (Evaluation Example 1 to 4) above. The results aresummarized in Table 4. TABLE 4 No. 1 2 3 4 5 6 7 8 Coating efficiency ∘∘ ∘ ∘ ∘ ∘ ∘ ∘ Evenness ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ Dispersion of pigments ∘ ∘ ∘ ∘ ∘∘ ∘ ∘ Adhesiveness ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ Water resistance coated ∘ ∘ ∘ ∘ ∘ ∘ ∘∘ surface (VE) adhesiveness ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ Possibility of recovery &reuse ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ Brightness ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ Alkali resistance ∘ ∘ ∘∘ ∘ ∘ ∘ ∘ No. 9 10 11 12 13 14 15 16 Coating efficiency ∘ ∘ ∘ ∘ ∘ ∘ Δ xEvenness ∘ ∘ ∘ ∘ ∘ ∘ ∘ x Dispersion of pigments ∘ ∘ ∘ ∘ ∘ ∘ x xAdhesiveness ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ Water resistance coated ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘surface (VE) adhesiveness ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ Possibility of recovery &reuse ∘ ∘ ∘ ∘ ∘ ∘ x x Brightness ∘ ∘ ∘ ∘ ∘ ∘ x x Alkali resistance ∘ ∘ ∘∘ ∘ ∘ Δ ΔVE: visual examination

As shown in Table 4, though the adhesiveness and water resistance of thecoated films from the powder paints (Nos. 15 and 16) prepared by the dryblending method were significantly high, the coating efficiency,evenness of the coated films, dispersion of pigments, and accordinglythe attractiveness of the coated films were lower because the pigmentparticles are not properly bound to the base paint powders. In addition,pigments in the coated films prepared from the powder paints recoveredand reused were more unevenly distributed, as the pigment particlesseparate easily from the base paint powders.

In contrast, the powder paints according to the present inventionprovided higher coating efficiency and coated surfaces favorable in anyof the evaluation tests and excellent in attractiveness of appearance,because the pigment particles are tightly bound to the base paintpowders. In addition, the surfaces of the coated films obtained by usingthe powder paints recovered and reused were equivalent or not inferiorto those of the first coated surfaces.

Example 2

An epoxy hardening-type polyester resin powder primer (Everclad No. 2100(brand name), Kansai Paint Co., Ltd.) was coated to a film thickness of80 to 100 μm onto an AC4C plate, which was previously chemicallyconverted with chromate (AL-1000 (brand name), Nihon Parkerizing Co.,Ltd.), by using an electrostatic powder coating machine GX-108. And theresulting layer was heated and hardened at 160° C. for 30 minutes toform a primer layer. Subsequently, powder paint No. 2 according to thepresent invention was coated over the primer layer to a film thicknessof 80 to 100 μm by using the electrostatic powder coating machine,GX-108, and the coated film was heated and hardened at 160° C. for 30minutes. The condition for electrostatic coating of the powder paint wasthe same as that in Example 1 above.

Example 3

A dodecanedicarboxylic acid hardening-type epoxy group-containingacrylic resin powder clear paint (Everclad No. 5600DK (brand name),Kansai Paint Co., Ltd.) was coated as a powder primer to a filmthickness of 80 to 100 μm onto an AC4C plate, which was previouslychemically converted with chromate (AL-1000 (brand name), NihonParkerizing Co., Ltd.), by using an electrostatic powder coating machineGX-108. And the resulting layer was heated and hardened at 160° C. for30 minutes to form a primer layer. Subsequently, powder paint No. 8according to the present invention was coated over the primer layer to afilm thickness of 80 to 100 μm by using the electrostatic powder coatingmachine, GX-108, and the coated film was heated and hardened at 160° C.for 30 minutes. The condition for electrostatic coating of the powderpaint was the same as that in Example 1 above.

Example 4

An epoxy hardening-type polyester resin powder primer (Everclad No. 2100(brand name), Kansai Paint Co., Ltd.) was coated to a film thickness of40 to 50 μm onto an AC4C plate, which was previously chemicallyconverted with chromate (AL-1000 (brand name), Nihon Parkerizing Co.,Ltd.), by using the electrostatic powder coating machine GX-108.Subsequently, without heat-hardening the primer layer, powder paint No.2 according to the present invention was coated over the layer to a filmthickness of 40 to 50 μm by using the electrostatic powder coatingmachine GX-108. And the primer and coated layer were heated and hardenedat the same time at 160° C. for 30 minutes. The condition forelectrostatic coating of the powder paint was the same as that inExample 1 above.

Example 5

Powder paint No. 2 according to the present invention was coated to afilm thickness of 80 to 100 μm onto an AC4C plate, which was previouslychemically converted with chromate (AL-1000 (brand name), NihonParkerizing Co., Ltd.), by using the electrostatic powder coatingmachine GX-108, and the resulting layer was heated and hardened at 160°C. for 30 minutes. Subsequently, an acrylic solvent-based clear paint(ALC-100 (brand name), Kansai Paint Co., Ltd.) was coated to a filmthickness of 30 to 40 μm by spray coating, and the resulting film washeated and hardened at 140° C. for 30 minutes to form a topcoat layer.The condition for electrostatic coating of the powder paint was the sameas that in Example 1 above.

Example 6

A coated film was formed from the appearance-improving powder paint inthe similar manner to Example 5 above. Subsequently a polyisocyanatecompound hardening-type acrylic solvent-based clear paint (Super DiamondClear Q (brand name), Kansai Paint Co., Ltd.) was coated to a filmthickness of 30 to 40 μm by spray coating, and the resulting film washeated and hardened at 80° C. for 30 minutes to form a topcoat layer.

Example 7

A coated film was formed from the appearance-improving powder paint inthe similar manner to Example 5 above. Subsequently adodecanedicarboxylic acid hardening-type epoxy group-containing acrylicresin powder clear paint (Everclad 5600DK (brand name), Kansai PaintCo., Ltd.) was coated to a film thickness of 80 to 100 μm by using theelectrostatic powder coating machine GX-108. And the resulting film washeated and hardened at 160° C. for 30 minutes to form a topcoat layer.The condition for electrostatic coating of the powder paint was the sameas that in Example 1 above.

Example 8

In the similar manner to Example 2 above, a coated film was formed overthe primer layer from the powder paints according to the presentinvention. And further an acrylic solvent-based clear paint (ALC-100(brand name), Kansai Paint Co., Ltd.) was coated to a film thickness of30 to 40 μm by spray coating, and the resulting film was heated andhardened at 140° C. for 30 minutes to form a top-coat layer.

Example 9

In the similar manner to Example 3 above, a coated film was formed overthe primer layer from the powder paints according to the presentinvention. And further a polyisocyanate compound hardening-type acrylicsolvent-based clear paint (Super Diamond Clear Q (brand name), KansaiPaint Co., Ltd.) was coated to a film thickness of 30 to 40 μm by spraycoating, and the resulting film was heated and hardened at 80° C. for 30minutes to form a top-coat layer.

Example 10

In the similar manner to Example 2 above, a coated film was formed overthe primer layer from the powder paints according to the presentinvention. And further a dodecanedicarboxylic acid hardening-type epoxygroup-containing acrylic resin powder clear paint (Everclad 5600DK(brand name), Kansai Paint Co., Ltd.) was coated over the layer to afilm thickness of 80 to 100 μm by using the electrostatic powder coatingmachine GX-108, and the resulting film was heated and hardened at 160°C. for 30 minutes to form a top-coat layer. The condition forelectrostatic coating of the powder paint was the same as that inExample 1 above.

Result 4

The evenness, adhesiveness, water resistance, brightness, and alkaliresistance of the coated films prepared in Examples 2 to 10 above wereexamined in a similar manner to the Evaluation Examples above. Theresults are summarized in Table 5. TABLE 5 Examples Evaluation item 2 34 5 6 7 8 9 10 Evenness ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ Dispersion of pigments ◯ ◯ ◯ ◯◯ ◯ ◯ ◯ ◯ Adhesiveness ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Water resistance coated surface(VE) ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ adhesiveness ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Possibility ofrecovery & ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ reuse Brightness ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Alkaliresistance ◯ ◯ ◯ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚VE: visual examination

As apparent from the results above, it was confirmed that the formationof primer or top clear layers in addition to the coated films from thepaint powders according to the present invention provides coatedsurfaces still more improved in the properties of coated films(especially, evenness and alkali resistance).

INDUSTRIAL APPLICABILITY

The powder paints obtained according to the present invention areexcellent in coating efficiency, as the constituents, base paint powdersand pigment particles, are bound tightly and do not separate duringcoating operation or the like. And the powder paints that have not beenadhered to the substrate can be reused, as the content of theseingredients is essentially identical to that of the original powderpaints.

In addition, the coated films from the bright powder paints producedaccording to the present invention have fine textured surface veryattractive in appearance and excellent in water resistance.

Therefore, the powder paints of the present invention can be used inwide applications, including industrial paint applications, givingcoated films for decoration or protection, and are very useful from thepractical viewpoint of economy and resource saving.

The process of producing powder paints according to the presentinvention has significantly high industrial utility, as it allowsproduction of the powder paints above.

Further, the processes of forming coated films and of producing coatedproducts according to the present invention are practically very usefuland can be applied to a wide variety of industry use, as they allowformation of excellent coated films for decoration or protection,especially when combined with primer and top clear layers, and allowproduction of coated products.

1-37. (canceled)
 38. A powder paint, characterized in that pigmentparticles therein are bound via shellac to base paint powders therein:39. The powder paint according to claim 38, wherein the content of theshellac is 0.01 to 1 mass % with respect to the total amount of thepowder paint.
 40. The powder paint according to claim 38, wherein theaverage diameter of the base paint powders is 10 to 100 μm.
 41. Thepowder paint according to claim 38, wherein the average diameter of thepigment particles is not more than 100 μm.
 42. The powder paintaccording to claim 38, wherein the powder paint contains a brightpigment as the pigment particle and the average diameter of the brightpigment is 2 to 100 μm.
 43. The powder paint according to claim 42,wherein the bright pigments are in the shape of flake and the thicknessthereof is 0.01 to 10 μm.
 44. The powder paint according to claim 38,wherein the powder paint contains an inorganic coloring pigment as thepigment particle and the average diameter of the inorganic coloringpigments is 0.01 to 5.0 μm.
 45. The powder paint according to claim 38,wherein the powder paint contains an organic coloring pigment as thepigment particle and the average diameter of the organic coloringpigments is 0.01 to 1.0 μm.
 46. The powder paint according to claim 38,wherein the powder paint contains a phosphorescent pigment as thepigment particle and the average diameter of the phosphorescent pigmentis 1 to 100 μm.
 47. The powder paint according to claim 38, wherein thecontent of the pigment particle is 0.1 to 50 mass % with respect to thetotal amount of the powder paint.
 48. A process of producing the powderpaint according to claim 38, characterized in that the process comprisesthe steps of: blending the base paint powder and the pigment particle;blending the resulting mixture with a liquid bonding auxiliary agentwherein shellac is dissolved in an organic solvent; and drying.
 49. Theprocess of producing the powder paint according to claim 48, wherein theliquid bonding auxiliary agent is blended using a mechanically agitatingblender in the blending step.
 50. The process of producing the powderpaint according to claim 48, wherein the liquid bonding auxiliary agentis blended using an airstream fluidized blender in the blending step.51. The process of producing the powder paint according to claim 48,wherein the liquid bonding auxiliary agent is added by spraying ordropwise addition.
 52. The process of producing the powder paintaccording to claim 51, the step of spraying the liquid bonding auxiliaryagent is carried out concurrently with the step of drying by supplyingair.
 53. The process of producing the powder paint according to claim52, wherein heated air is used as the air.
 54. A process of forming acoated film, characterized in that the coated film is formed byelectrostatic powder coating of the powder paint according to claim 38onto a substrate made of metal material.
 55. The process of forming acoated film according to claim 54, wherein a primer layer is formed inadvance to the electrostatic powder coating.
 56. The process of forminga coated film according to claim 55, wherein the primer layer is formedwith a powder paint.
 57. The process of forming a coated film accordingto claim 56, wherein the primer layer is formed with a powder painthaving an epoxy resin hardening-type polyester resin or acidhardening-type epoxy group-containing acrylic resin as the maincomponent of the base paint powder.
 58. The process of forming a coatedfilm according to claim 54, wherein an additional top clear layer isformed over the coated film.
 59. The process of forming a coated filmaccording to claim 58, wherein the top clear layer is formed with anacrylic solvent-based clear paint or acrylic powder-based clear paint.60. The process of forming a coated film according to claim 59, whereina polyisocyanate hardening-type clear paint is used as the acrylicsolvent-based clear paint.
 61. The process of forming a coated filmaccording to claim 59, wherein an acid hardening-type clear paint havingepoxy groups is used as the acrylic powder-based clear paint.
 62. Theprocess of forming a coated film according to claim 59, wherein a clearpaint, having an epoxy group-containing acrylic resin as the base resinand containing a polycarboxylic acid as a curing agent, is used as theacrylic powder-based clear paint.
 63. The process of forming a coatedfilm according to claim 62, wherein dodecanedicarboxylic acid is used asthe polycarboxylic acid.
 64. A process of producing a coated productcoated with a powder paint, characterized in comprising a step ofcoating the powder paint according to claim 38 onto a substrate made ofmetal material by electrostatic powder coating.
 65. The process ofproducing a coated product according to claim 64, further comprising astep of forming a primer layer onto the substrate in advance to theelectrostatic powder coating step.
 66. The process of producing a coatedproduct according to claim 65, wherein the primer layer is formed with apowder paint.
 67. The process of producing a coated product according toclaim 65, wherein the primer layer is formed with a powder paint havingan epoxy resin hardening-type polyester resin or acid hardening-typeepoxy group-containing acrylic resin as the main component of the basepaint powder.
 68. The process of producing a coated product according toclaim 64, further comprising a step of forming a top clear layer as theutmost outer layer.
 69. The process of producing a coated productaccording to claim 68,wherein the top clear layer is formed with anacrylic solvent-based clear paint or acrylic powder-based clear paint.70. The process of producing a coated product according to claim 69,wherein a polyisocyanate hardening-type clear paint is used as theacrylic solvent-based clear paint.
 71. The process of producing a coatedproduct according to claim 69, wherein an acid hardening-type havingepoxy groups is used as the acrylic powder-based clear paint.
 72. Theprocess of producing a coated product according to claim 69, wherein aclear paint, having an epoxy group-containing acrylic resin as the baseresin and containing a polycarboxylic acid as a curing agent, is used asthe acrylic powder-based clear paint.
 73. The process of producing acoated product according to claim 72, wherein dodecanedicarboxylic acidis used as the polycarboxylic acid.
 74. A coated product, characterizedin being produced by the process according to claim
 64. 75. A coatedproduct, characterized in being produced by the process according toclaim
 65. 76. A coated product, characterized in being produced by theprocess according to claim
 66. 77. A coated product, characterized inbeing produced by the process according to claim
 67. 78. A coatedproduct, characterized in being produced by the process according toclaim
 68. 79. A coated product, characterized in being produced by theprocess according to claim
 69. 80. A coated product, characterized inbeing produced by the process according to claim
 70. 81. A coatedproduct, characterized in being produced by the process according toclaim
 71. 82. A coated product, characterized in being produced by theprocess according to claim
 72. 83. A coated product, characterized inbeing produced by the process according to claim 73.